In order to achieve accurate segmentation of each grape image per berry, we construct a dataset composed of red globe grape samples and use a two-stage “localization–segmentation” framework-based mask region convolutional neural network (Mask R-CNN) and one-stage “pixel classification without localization” framework-based You Only Look At CoefficienTs (YOLACT) and segmenting objects by locations (SOLO) models in the grape segmentation experiments. The optimal performance of the model Mask R-CNN was applied for further study. To address the problem of overlapping and occlusion causing inaccurate fruit detection in this model, the postprocessing algorithm of the Mask R-CNN model was improved by using the linear weighting method, and the experimental results were significantly improved. The model average precision (AP)_0.50, AP_0.75, the mean average precision (mAP), and the mean intersection of union (mIoU) improved by 1.98%, 2.72%, 4.30%, and 3.55%, respectively. The correlation coefficient was improved from 93.59% to 96.13% by using the improved Mask R-CNN to count the number of red globe grape berries, which also further illustrates that the fruit detection problem was well solved. Using the generalized method on untrained images of different grape varieties in different scenes also achieved good segmentation results. In this study, we provide a method for segmenting and counting grape berries that is useful for automating the grape industry.

The measurement of grape sugar content is an important index for classifying grapes based on their quality. Owing to the correlation between grape sugar content and appearance, non-destructive measurements are possible using computer vision and deep learning. This study investigates the quality classification of the Red Globe grape. The number of collected grapes in the range of the 15~16% measure is three times more than in the range of 18% measure. This study presents a framework named feature normalization reweighting regression (FNRR) to address this imbalanced distribution of sugar content of the grape datasets. The experimental results show that the FNRR framework can measure the sugar content of a whole bunch of grapes with high accuracy using typical convolution neural networks and a visual transformer model. Specifically, the visual transformer model achieved the best accuracy with a balanced loss function, with the coefficient of determination R = 0.9599 and the root mean squared error RMSE = 0.3841%. The results show that the effect of the visual transformer model is better than that of the convolutional neural network. The research findings also indicate that the visual transformer model based on the proposed framework can accurately predict the sugar content of grapes, non-destructive evaluation of grape quality, and could provide reference values for grape harvesting.